Telegraphic line circuit



Aug. 13, 1940. J. SINGER 2,211,176

TELEGRAPHIC LINE CIRCUIT Filed Jan. 26, 193B 6 Sheets-Sheet 1 FIG /0 FIG. H6- a Flat:

FIG 7 F/G.4 FIG. FIG. 3 FIGS F/GJ Ha: FIG.3

Q \3 '5 INVENTOR 1". J. S/NGL R 147' TORNE V Aug. 13,' 1940.

- TELEGRAPHIC LINECIRCUIT Filed Jan. 26, 1958 6 Sheets-Sheet 3 a g 5 E g I36" 1 um 2" I FIG. 3 h

lA/l/EA/ 70/? E J. SINGER F. J; SINGER 2,211,176

AT TORNE) J. SING ER I 2,211,176 TELEGRAPHIC LINE CIRCUIT I 6 Sheets-Sheet 4 Filed Jan. 26, 1938 lA/VE/VTOR E J. swam A7 TORNEV FIG. 6

Aug. 13, 1940- F. J. SINGER 2,211,176

TELEGRAPHIC LINE CIRCUIT Filed Jan. 26, 1938 6 Sheets-Sheet 5 lNVEA/TOR By E J. SINGER AT TOR/V5) ANS.

F. J. SINGER TELEGRAPHIC LINE CIRCUIT Aug. 13, 1940.

6 Sheets-Sheet 6 Filed Jan. 26, 1938 lNI/ENTOR F J. swam ATTORNEY jaw I. I km, 1 E

Patented Aug. 13, 1940 UNITED STATES anti? rnr its TELEGRAPHIC LINE omoorr Application January 26, 1938, Serial No. 186,963

17 @laims.

This invention relates to long telegraph or teletypewriter line circuits used to connect remote subscribers stations to central telegraph or teletypewriter exchanges. These circuits are known in the art as subscribers toll line extension circuits to distinguish them from simple subscribers loops.

An object of this invention is to provide improved supervisory features on subscribers long extension line circuits involving either single or multisection repeaters. It makes use of the full duplex feature of a multisection two-path polar circuit to obtain the desired supervisory signaling arrangements. It is not limited to such a circuit but will function equally well with any full duplex telegraph single or multisection circuit such as carrier, metallic and grounded duplex systems as well as single section two-path polar systems.

In all multisection repeater subscribers line circuits known to the applicant where the portion of the circuit extending from the subscribers station to the first repeater point is limited to one pair of wires the system operates on a closed loop basis. That is tosay, that portion of the circuit between the station and the first repeater point is closed and current flows continuously through the subscribers loop. In order to signal the operator at the central station, the subscribers loop is momentarily opened at the subscribers station for an interval sufficient to lock in a relay controlling a calling signal, usually a lamp, at the central station. After the relay locks in, the calling signal is no longer under control of the apparatus at the subscribers station. If the subscriber wishes to abandon the call, he cannot do so before the operator responds at the central station. This objection is overcome by the present invention.

There are other disadvantages to the closed loop. If a continuous break signal is being received at the subscribers station due to a trouble condition either in the extension circuit or in the connecting circuit beyond the central station, there is no means by which the subscriber operating on a closed loop may signal the central staan open circuit between the subscribers station and the first point on the receiving channel where battery is normally applied to the subscribers loop.

A feature of this invention is that the calling line signal of a multisection repeater telegraph extension line circuit may be operated and restored to the idle condition under complete control of the subscribers station.

A further feature of this invention is that two generally independent channels are provided connecting the subscribers station and the central station, one for transmitting and one for receiving. Call, recall and disconnect signaling is performed over the transmitting channel which is substantially independent of the receiving channel. Therefore, the subscriber may signal the central station if his transmitting channel is operative as far as the central station, even though the extension circuit receiving channel and connections beyond the central station may be in trouble.

A further feature of this invention is that whereas signals of various intervals are used for supervisory purposes, discrimination between them is accomplished on the station side of the 2 switchboard while the line beyond is closed, thus preventing possible mutilation of time signals originating in connecting circuits.

A further feature of this invention is the incorporation of the feature of the foregoing para- 3 graph in a subscribers extension station circuit comprising a plurality of repeater sections.

A further feature of this invention is that while discrimination between the various supervisory signals is accomplished on the line side of the switchboard, break signals readily pass between subscribers station and subscribers station through the connecting circuits.

A further feature of this invention is that recall and disconnect signals may be transmitted from the subscribers station to thecentral station, even though at the same time a break signal is being received at the subscribers station.

The invention will be readily understood from the following detailed description made with reference to the accompanying drawings, in which:

Fig. l is a two-path polar multisection repeater telegraph extension line circuit with a subscribers loop normally open when idle; 5

Fig. 2 is a cord circuit together with its associated operators position circuit illustrative of a means of interconnecting Fig. l with a connecting circuit. The connecting circuit may be either a second subscribers line circuit or a trunk Q circuit to a second telegraph ofiice. The second line circuit may be either a simple telegraph subscribers loop circuit or an extension line circuit. The trunk may be either a local or a long distance, frequently called toll trunk to a second central station;

Fig. 3 is identical with Fig. 1, except that it is shown reversed to better illustrate the interconnection of two multisection repeater telegraph extension line circuits when interconnected by means of a cord circuit;

Fig. 4 is a second cord circuit illustrative of a second type of cord with which Fig. 1 and Fig. 3 will function;

Fig. 5 is the operators position circuit associated with Fig. 4;

Fig. 6 is a third cord circuit illustrative of a third type of cord with which Fig. l and Fig. 3 will function. In so far as Fig. 6 cooperates with Fig. 1 and Fig. 3 to provide supervisory signals it is in general similar to the cord of Fig. 2;

Fig. '7 is the operators position circuit associated with Fig. 6;

Fig. 8 is a diagram indicating in block form the interconnection of Fig. l and Fig. 3 by Fig. 2;

9 is a diagram indicating in block form the interconnection of Fig. l and Fig. 3 by Fig. 4 and Fig. 5; and

Fig. 10 is a diagram indicating in block form the interconnection of Fig. l and Fig. 3 by Fig. 6 and Fig. '7.

The connections illustrated involve one central station only. Trunk connections are not shown because it is believed that they are not necessary to an understanding of the present invention.

Refer now to Fig. l. A two-path polar subscribers extension line circuit is shown together with its associated terminating circuit. At the extreme left of Fig. 1 a subscribers station teletypewriter circuit is shown according to the usual conventions. The circuit is shown in the idle con dition with the station loop, indicated by the heavy line, open at power switch lI. Key I09 is used to transmit a disconnect signal to the central station. When operated, it opens and closes the associated contacts three times to send a series of three one-half second pulses. Keys H0 and I40 are alternative recall keys. One or the other is connected to the circuit depending upon the type of cord circuit used at the central office to cooperate with Fig. 1. When key III) is in circuit and operated, it sends a series of four pulses, the first three being one-half second pulses and the fourth a one-second pulse. When key I40 is in circuit and operated, it sends a series of four one-half second pulses. When key M0 is in circuit, switches IM and I42 are operated to engage contacts I44 and I45, respectively. Only one of the two keys, namely, H0 and I40, is connected into the circuit at a particular time. With switches MI and I42 in their present positions as indicated on the drawings, namely, in engagement with contacts I43 and I45, respectively, key H0 is connected and key i 40 is disconnected. When switches IQI and I42 are operated to engage contacts I44 and I46, respectively, key I60 is connected into the circuit and key III) is disconnected from the circuit. Interrupter I32 is required only when key M0 is in circuit. Under these circumstances switch I39 is operated so as to connect interrupter I32 to selector bank !25.

The three dotted rectangles to the right of the subscribers station equipment include relay resistance and battery equipment at successive repeater stations intermediate the subscriber's local station and the teletypewriter central switching station.

The equipment to the right of the three dotted rectangles represents the terminating circuit at the teletypewriter central switching station. The component parts of a two-bank selector in the terminating circuit comprise rotary magnet I22, release magnet I2l, selector banks I25 and I26 and off-normal springs E38. When rotary magnet I22 is energized, it rotates both of the arms associated with the selector banks I 25 and I26 so that the arms make contact successively with corresponding terminals on the banks as far as the rotary magnet drives them. The bank terminals are represented by the two groups of small circles arranged in the form of arcs. Normally, as indicated, the selector arms do not make contact with the bank terminals. When the arms are stepped from the normal position shown, the off-normal springs are actuated to close, extending the circuit from battery through the winding of release magnet I2I. When ground is connected to this circuit at the proper juncture, the bank arms are restored to their normal condition.

Fig. 1 is arranged to be operated in either of two ways to provide the flashing lamp recall feature to be described hereinafter. It is arranged so that the flashing lamp in the cord may be operated by an interrupter located either in the extension line circuit or by an interrupter in the cord. 7 With cords such as Fig. 2 and Fig, 6, the interrupter in the extension line circuit, Fig. l, is not used. With cords such as Fig. 4, the interrupter in the line circuit is used.

The method of operation of Fig. 1 will now be described in detail. The circuit as shown is in the idle condition. During this condition current drains through the biasing windings of relays I21, I29 and H3. Current drains also through the spacing contact of relay I29 and winding of relay I30 and through the spacing contact of relay H3 and winding of relay II4.

A. Subscriber calls To call, the subscriber at the local teletypewriter station operates power switch IOI to the left to close the two make contacts. Power is supplied from the ll0-volt alternating current power source I03 through power switch IOI, left hand make contact to the lower terminal of the rectifier I04 and the upper brush of motor I02 in parallel. From the other side of the power source I03 power is furnished to the upper terminal of rectifier I 04 and the lower brush or motor I02. llO-volt alternating current is connected to the teletype motor and to the alternating side of the rectifier. Direct current is connected to the upper or biasing winding of polar relay I and to magnet I06. The teletypewriter keyboard is locked open as an open signal is received from the switchboard end of the circuit, The operation of power switch l0! also closes the loop to the nearby central ofiice containing the telegraph repeater. The circuit through ringer I3l is broken at the break contact of power switch IOI. We will assume that switches MI and I42 are on contacts I 43 and I45 respectively so that key H0 is in circuit and key I40 is disconnected. Negative ail-volt battery flows through relay I08 winding, disconnect key I03, break contact, recall key H0, break contact, teletypewriter sending contacts I01, lower winding relay I05, righthand make contact power switch I0 I, upper winding relay II I through the armature and S contact relay I30 to I30-volt negative battery. This current is of about 25 mils and in a direction to operate relay III to S but the current through the lower winding relay III, of about 42 mils, holds the armature on M. Relay I08, however, operates, furnishing ground to relay H2, which also operates.

The operation of relay I I2 closes a circuit from positive I30-volt battery through the M contact and armature relay II I, make contact relay I I2, upper winding relay H3 to negative I30-volt battery. The current through the upper winding of relay I I3, of about 60 mils, opposes the biasing current, of about 30 mils, in the lower winding and the relay operates to M.

Operation of relay H3 to M furnishes I30-volt negative battery to relay H4 winding, operating relay I I4 to M. Operation of relay I I4 to M closes a circuit from negative I30-volt battery through the upper winding relay H5 to ground and a parallel circuit through relay III; also to ground, operating both relays. When relay IIB operates it prepares a circuit for the operation of relay II'I from battery through relay III winding, armature and front contact relay IIS to the lower front contact relay I20 which is open at this time so that relay II'I does not operate. The operation of relay II5 closes a circuit from negative I30-volt battery through the M contact and armature relay I I5, upper armature and back contact relay I20 through relay IIO winding, operating relay I I8. The operation of relay I I8 lights lamp, I I 9 over an obvious circuit.

B. Operator answers To answer, the operator inserts the answering plug of a cord circuit which we will assume to be plug 224 of Fig. 2 into jack I20. Battery is supplied through the cord circuit sleeve, jack I28 sleeve to the winding of relay I20, operating the relay. The operation of relay I20 closes a circuit from ground through the lower armature and front contact relay I22, through the front contact and armature relay H6, through relay II'I winding to battery. Relay II'I operates. The operation of relay II'I removes ground from the selector release magnet IZI. The operation of relay I20 also prepares a circuit from ground through the lower armature and front contact relay I20 to the open break contact relay IIB for the operation of the selector rotor magnet I22. The operation of relay I20 also breaks the path over which relay IIB was operated at its upper armature and break contact. Relay IIB releases, extinguishing lamp I I9. The operation of relay I20 closes a circuit from negative l30-volt battery through the M contact and armature relay II5 through the upper armature and make contact relay I20 and relay I23 winding to ground, operating relay I23. The operation of relay I23 closes a circuit from battery through relay I23 armature and front contact through relay I24 winding to ground, operating relay I24. The operation of relay I24 removes ground from the ring circuit of jack I23 at the lower inner back contact relay I24 and connects the ring through the lower inner armature and front contact relay I24 to the rotor associated with selector bank I25. Operation of relay I24 also connects positive battery through its lower outer armature and front con tact to the S contact relay H5. Operation of relay IE I also transfers the apex of relay I27 from lBO-volt negative battery at relay I2 3 upper outer armature and back contact to negative I30-volt battery through the M contact and. armature relay II5, back contact and armature relay I38, upper inner armature and front contact and upper outer armature and front contact relay I24.

Since positive battery is connected to the tip of the jack through one side of the cord circuit repeater in the switchboard, current of about 60 mils flows through the upper winding relay I2'I over the path last traced to negative I30-volt battery on the M contact relay II5. This current is in a direction to operate relay I21 to its M contact and overcomes the biasing current, about 30 mils, flowing through the lower winding relay I27. Relay I2'I therefore operates to M. Operation of relay I 27 to M closes a path from -volt positive battery through the M contact and armature relay I21 through the upper winding relay I29 to negative battery, operating relay I29 to M. The operation of relay I20 closes a path from I30-volt positive battery through the M contact and armature relay I29 through the winding relay I30 to ground, operating relay I30 to M.

When relay I30 is operated to M positive, 130- volt battery is furnished through the M contact and armature relay I30 to the apex of relay III and over the loop heretofore traced to negative iS-volt battery connected to the winding relay I08. This current operates the polar station relay III5 to M and the subscriber at the local station is now in a position to communicate with the operator at the central station. When the subscriber sends a spacing signal from the teletypewriter, the resistance I33 prevents current in the loop from dropping" to zero and relay I08 remains operated. The current, however, is of small value and the 42 mils biasing current in the lower winding of relay II causes relay III to operate to S.

A break circuit is provided from negative 130- volt battery through the lower winding relay I I5 to the S contact relay IN to permit breaking the subscriber if the subscriber is sending. A break key in the subscribers station loop permits the subscriber to break a sender on the switchboard side cf the line.

C. Operator calls station To call the subscriber the operator at the central station inserts the plug associated with the calling end of her cord circuit into jack I 28 of Fig. 3. Ground is furnished from the lower inner back contact relay I24 through the associated armature through jack I28 ring into the ring of the cord. This causes a relay in the ring circuit of the cord to operate and light the cord lamp indicating that the subscriber has not yet answered. Since Figs. 1 and 3 function with various types of cords, the operation of the cords is discussed separately below. Battery is furnished over the sleeve circuit of the cord to jack I28 sleeve through relay I20 winding to ground, operating the cord circuit sleeve relay and relay I2fi. Positive battery is connected to the tip of jack I28 through the teletypewriter cord circuit repeater in the cord. This positive battery meets negative 130-volt battery through the upper winding of relay I21" from the upper armature and back contact of relay IN. A current of 60 mils flows through this winding causing relay IZI to operate to M and the cord circuit and operators teletypewriter to close up. Operation of relay I21 to M causes relay I29 to operate to M which in turn operates relay ISO to M. Relay I30 on operation to M causes relay III to operate to M. The operation of relay I I I, however, is ineffective to operate relay H3 at this time as relays I12 and IE6 are not operated. Relays H3, iii and HE, therefore, remain on S. Relays i23' and do not operate. The operation of relay E20, previously described, prepared a circuit for the operation of relay but as there is no battery on the S contact of relay I I5, relay lid is unopersted, relay l2S cannot operate.

The operator rings the station by connection :i=l)5-volt ring current to the tip of the cord. Relays 27, iQQ, 38 and ill follow these pulsesand ringer iSi ultimately responds from the positive and negative ZBQ-volt reversals through the armature of relay i236, upper Winding of relay l i l, right-hand break contact of the power switch Hit, the switch being unoperated at this time through condenser I35 and the ringer I3l in ground.

The subscriber answers by operating power switch IIlI. This close: the station loop circuit operating relays I98 and H2 as heretofore de scribed. Relay Iii stops operating even though ringing pulses are still being sent. Therefore, the positive l30-volt battery is now connected through relay III armature, relay IIi. contact, through the upper winding of relay I it to negative battery operating relay M3 to M. In turn, relays H6, H5, H8 and Ill operate. Operation of relay II5 completes the circuit to relay I23 over a path from negative battery through the M contact and armature relay H5, upper armature and front contact of relay 25 through relay I23 winding to ground. The operation of relay furnishes battery through its armature and make contact through relay I2 winding to ground, operating relay 224'. When relay i2 5 operates ground is removed from the ring circuit at its lower inner back contact and armature and the cord lamp is extinguished, indicating to the operator that the subscriber has answered. Operation of relay I24 also connects positive l30-volt battery to relay H5 S contact. It also replaces holding negative l3il-volt battery which has been furnished through the upper outer back contact and armature relay I24 to relay I27 apex by negative l30-volt battery from relay EIE' M contact and armature through the back contact and armature relay I33, upper inner armature and front contact relay I2 i, upper outer front contact and armature relay 926 to relay I21 apex. The circuit is now ready for communication.

D. Subscriber breaks If during communication the subscriber Fig. 1 wishes to stop the sending of the distant subscriber or switchboard operator, he opens his break key I36 for one or more seconds. This causes relay I88 and relay H2 to release. Relays H3, H4, H5 and IIS also release regardless of whether relay I36 is on M or S at this time. Release of relay H5 to S connects positive 130- volt battery through the lower outer armature and front contact relay I26, S contact and armature relay IE5, back contact and armatiu'e relay l33, upper inner armature and front contact and upper outer front contact and armature relay I 2 3 to relay I27 apex. When the next marking signal is sent from the cord positive l30-volt battery in the cord meets this positive l30-volt battery furnished t0 the apex of relay E2 and no current will flow in the cord. A break is therefore obtained.

About one-third second after relay II i has operated to S, relay I I6 releases since it is shunted by rectifier I34 which short-circuits it for current from positive l30-volt battery. Release of relay H6 closes a circuit from ground through relay I20, lower armature and front contact, relay IIB break contact through the winding of the selector rotary magnet I22 to battery energizing this magnet. After another one-third second relay I ll releases connecting ground through relay II'I, armature and front contact to the contact of the off-normal springs I38 to battery. As the selector off-normal springs I38 are not operated until the selector steps from the normally unoperated position, the release magnet is not energized at this time.

When the subscriber releases break key I36, the loop again closes and relays I08, H2, H3, H4, II 5, H6 and II! reoperate. Operation of relay HG opens the circuit of selector rotary magnet 22 and the selector rotary arms associated with selector banks I25 and I26 step to the first bank contacts. It will be observed that no electrical operations ensue as a result as no wiring is connected to the first contact on either bank I25 or I26. The oif-normal contacts of the selector I38 are operated to furnish battery to the release magnet and as relay I I1 is released a path is provided to ground through relay II? back contact and armature. The release magnet operates to restore the selector to normal. Relay l i I winding is shunted by condenser 37 to slow up the operation of relay I I7 sufnciently to prevent its operation after relay H6 operates, before selector rotary magnet I22 has stepped the selector to the first contacts on the banks.

E. Subscriber recalls or disconnects The subscriber may send a recall or disconnect signal to the switchboard operator after a connection is established by operating recall keys Iii] or I 4-8 depending on the type of cord used or disconnect key H39. These signals will be received at the central station regardless of whether the subscriber is at that time receiving a break signal from the line since when either of these keys is operated it controls relay I08. Three one-half second open and close pulses are sent from key I09 for the disconnect signal to the switchboard and three one-half second open and close pulses followed by a long open pulse will be sent from key lIil as a recall signal. When key I49 is used four one-half second open and close pulses are transmitted. For each one-half second open, relays I88 and II2 release, equivalent open or break signals are sent over the line. Since these one-half second opens are not of sufficient length to permit relay II? at the central office to release because relay I I7 does not start releasing until relay US has released, the selector release magnet circuit remains open and the selector rotary magnet causes the selector to step in accordance with the signal pulses received. The first open pulse is transmitted through relay I21 to the cord circuit and to the toll line or line circuit beyond depending on the type of connection and it will be long enough to interfere with the long open signals if any are being sent at that time over the toll line. Subsequent one-half second opens will be blocked, however, since relay I3B operates as soon as the selector reaches the second point on selector bank I26 from ground through the selector arm through the second, third or fourth contact on bank I26, through relay I38 winding to battery. Operation of relay I38 cuts and closes relay I21 apex to 130-volt negative battery so that it no longer responds to relay I I5.

If a recall signal is being sent from the station when key I is used and the interrupter is in the associated cord circuit, the four open and close pulses cause the selector to step to the fourth point where ground at 60 interruptions per minute is applied from interrupter I32 to the fourth contact of selector bank I25 and the selector arm associated therewith through the lower inner front contact and armature relay I24 to the ring of jack I28 and thence to the ring of the cord circuit. This circuit causes the cord lamp to flash. To extinguish the lamp the operator momentarily shunts relay Hill by operating a key in the cord. The shunting of relay I20 releases it and furnishes ground to the selector release magnet through relay I20 lower armature and front contact. The selector, therefore, restores to normal.

If, however, key Eli! is being used, when the extension circuit is functioning with a cord having an interrupter, at the end of the third pulse transmitted by key Hi the selector will have stepped to the third point on the banks. Ground will be furnished through the third contact on bank 625 through the lower inner front contact and armature of relay I24 to the ring of iack 28. On the next pulse, which will be long, relay HE will release, the selector will step to the fourth point on the bank. Then relay It! will release and the selector will be returned to normal. As soon as the selector leaves the third point, ground will be removed from the ring of the cord and the cord lamp will flash. The operation in the cord will be further described below.

If a disconnect signal is being sent from the station, the three open and close pulses cause the selector to step to the third contacts on the banks. Permanent ground is furnished through the third contact on selector bank 525 through the associated selector bank arm, lower inner front contact and armature relay i2 3, over the ring of jack E28, to the ring of the cord circuit 528 is used for supervisory purposes.

connected thereto. This ground causes the cord lamp to burn steadily. The operator thereupon pulls down the cord, releasing relay we and in turn selector release magnet i2! is energized and the selector is restored to normal.

Reference to Fig. 1 and the foregoing description indicate that the tip conductor at jack I728 herein is used for transmitting the positive and negative battery communication signals and the break signal which isa relatively long pulse of positive battery. The ring conductor herein at It is arranged to furnish steady ground to a lamp relay in the ring of any cooperating cord as a disconnect signal. As to the recall signal, the ring is arranged to furnish interrupted ground to the same cord lamp relay directly in one type of cooperating cord to provide a flashing lamp, or to furnish temporary ground followed by an open to a second type of cooperating cord to transfer the cord flashing lamp from the steady '1 lamp disconnect relay to a relay supplying interrupted ground in a manner well-known in the art. The sleeve of the jack furnishes ground through relay 82E winding to cooperate with a cord supplying battery directly or through relay windings or contacts to perform such cord functions as may be required.

It will be observed that the ring circuit at the jack which controls supervision is independent of the receiving branch of the line circuit. This ,permits the, subscriber to. receive a break signal which could result from a trouble condition in connecting circuits without interfering with a recall or disconnect signal sent by him to the local operator.

Further recall and disconnect signals, though generated on a time basis in the tip loop conductors on the subscribers side of the switchboard, do not involve protracted tying up of circuits beyond the switchboard as they are translated into conditions furnished to the ring of the jack circuit. Hence, there is no mutilation of recall or disconnect signals transmitted between switchboard operators on toll connections.

It is apparent from the above, that timed supervisory signals generated at the local station are transmitted over one of the subscribers loop conductors to the central station at which the switchboard is located. There the timed signals are translated into conditions applied to a con necting conductor other than the conductor used to transmit communication and break signals, while the transmission circuit is closed. The conductor to which the conditions have been applied is used to control a supervisory signal circuit local to the switchboard.

The long telegraph or teletypewriter line circuit disclosed herein therefore will function with any of a number of cord circuits arranged to cooperate with the three conductors comprising the jack circuit herein, by arranging the corresponding cord conductors to cooperate with the conditions supplied to the long line circuit jack in any of many manners well known the art.

In Figs. 8, 9 and 10, the line circuit of this invention is shown cooperating with three different types of cord circuits, together with their respective position circuits. In Fig. 2, the cord and position circuit are included in the one figure. Fig. 4 shows a second type of cord and Fig. 5 its associate position circuit. Fig. 6 shows a third type of cord and Fig. '7 its associated position circuit. These cord and position circuits, in cooperating with the extension line circuit of this invention, function in their usual well-known manner, but their operation will now be described as far as it is necessary to show their relationship to the new circuit of this invention.

In the case of Fig. 8, when Fig. 2 is used with Fig. 1 and Fig. 3, before plug 22 of Fig. 2 is inserted in jack MB of Fig. l, in response to the lighted signal lamp, M9, the typing key T is operated to its upper contact. Relay 205 operates from ground through the key armature and upper contact, winding relay 2% to battery, connecting the operators position circuit to the cord. The transmission circuit is open, however, since relays 2M and M3 are not operated. Relay EU is on its S contact under control of current through its lower winding. Relay winding SM is short-circuited and the teletypewriter magnet 3533 is closed, preventing the teletypewriter mech anism from spinning. Since the transmission circuit is open operating the position circuit teletypewriter keyboard contacts has no effect on the mechanism.

The operator inserts the answering cord plug 224% into the extension station line jack I28 of Fig. 1 to answer the call. Relays 2!]! and 292 in the answering cord and relay 82!! in the station line circuit are connected in series and operate over a circuit from battery, through relay 2GB winding, lower winding relay 202, sleeve of plug 224, sleeve of jack H28, winding of relay I20 to ground. All three relays operate. The sequence of events in the extension line circuit following the operation of relay 526 has been heretofore described. In the cord circuit per 2, the operation of relay 2M closes a circuit relay 26 which operates. Operation of relay rnnot s battery from relay 2% winding, preve ring it from operating even though relay Ziil has operated.

/hen relay operates, the ring circuit of $28 is connected through the lower break of relay 8 to relay 2S? winding. Relay s not operate since relay 2 1 in the extenline circuit is operated removing ground from the ring.

The operation of relay 2% also connects the tip circuit of jack E28 through the tip of plug make-before-bre'ik contact of relay 28 3, top outer make-before-break contact of relay 265, conductor 22E, break contacts of ringing key RA, break contacts of C portion of splitting key, SP, teletypewriter keyboard contacts, break key, upper winding relay 30!, break contact of A portion of splitting key, SP, conductor 23-), top inner armature front contact relay 2%, upper winding relay 2H, to positive battery through M contact of relay 2H2. The transmission circuit to the extension circuit is therefore closed from negative battery on the armature of relay M5 to positive battery on the contact of relay H2. The station and operators teletypewriters are connected. Relay 36! operates to M and relay 3H2 operates. The operators keyboard is no longer locked and the magnet is under control of relay 39!. The operator and station subscriber may now communicate. Relay also clos-ed a circuit from battery through its bottom arma are and front contact through relay 3E3 wind ng to ground operating relay 2H3. Relay also closed a circuit from ground through its outer armature and front contact through the top winding of relay 2m to positive battery. It also closed a circuit from ground through the same top outer armature and front contact to both windin s of relay 255, the circuit through the bottom winding being extended from junction point 23! over conductor 233, through the top inner armature and back contact of relay 2 5? through relay 2 is bottom winding to positive battery. Relay 26E} operates when relay 2H operates to M and connects ground to the bottom winding of relay 2m. Since the ampere turns through the bottom winding of relay Zlil are greater than those through its top winding relay 2m operates to M, even though the current through the top winding is in a direction to operate to S. Relay 2l6 operates to M since ampere turns through its top winding are ater than through its bottom winding.

Operation of relay connects ground to the bottom winding of. relay 2H and the middle winding of relay 222 through the left and right and inner armatures and front contacts respectively. Relay 253 also connects negative battery through its right and outer armature and front contact upper outer break contacts of relay 2E9, upper outer break contacts of relay M8 and ill to the top winding of relay 292. The current through the bottom winding of relay 2H and middle of relay 252 are in a direction to cause these relays to operate to S. The currents through the top windings of these relays are in a direction to hold the relays on M and since the effective ampere turns in the top windings are twice as great as those in the bottom winding of reiay EH and middle winding of relay 222 the armatures of relays 2| l and H2 remain on their M contacts.

Since the extension line circuit is multipled throughout the switchboard, there may be several operators attempting to answer the call when the line lamp H9 lights. The cord relays 282 and 253 in the cord which establishes the connection prevent this from happening. When several cords are plugged in simultaneously, one cord makes the connection and relays 295 and 282 operate as described above. As soon as relay 202 has operated, a low resistance battery shunt through the top winding of relay 2512 is connected to the sleeve of plug 224. This shunt raises the potential of the sleeve to a value which prevents the 262 relays of other cords from operating. The 25! and 202 relays, in the cord which has become connected, remain operated. In each of the other cords relay 26! only operates and its operation causes relays 2513 and 204 to operate. Relay 2M operates over a path from ground through the armature and front contact of relay 231, through 2M- winding to battery. Relay 233 operates from ground through the same armature and front contact of relay 20l through the winding of relay 2% back contact and armature of relay 2S2 to battery. In each of these cords, positive battery is therefore connected to the tip circuit through the upper armature and front contact of relay 2G3 and the upper middle armature and front contact of relay 204. This potential is equal to that established from the M contact of relay 2P2. The top winding of relay Sui in each of these operators position circuits is therefore shunted and does not operate to M. Relay 382 does not operate and the keyboard is locked. The positive battery connected to the tip circuit in each of the lock-out cords also shunts out the 32! relay in the operators position circuit of the cord that has obtained the connection and that operator cannot communicate. Since relay 293 is not operated in the cord which establishes the connection, but is operated in all other cords in the multiple, the position pilot lamps, 22?, of the interfering cords are lighted. These operators then remove their cords. When all interfering cords have been removed, the remaining cord can be used by the operator to communicate with the subscriber.

After the calling subscriber has passed the number of the called subscribers station to the teletypewriter switchboard operator, the operator is ready to complete the call. She first tests the called subscribers line in the well-known manner to see if it is busy at another operators position. The Well-known busy test connections in the cord are not shown. If the subscriber's line is not busy, the operator first operates her typing key T and then inserts plug 226 of Fig. 2 into jack E28 of Fig. 3. Fig. 3 and Fig. l are identical except that as an aid in visualizing the interconnection, the calling line, the cord, and the called line have been indicated as a chain connection of three figures by reversing Fig. 1 and assigning to it a new figure number, Fig. 3, when it serves in the capacity of a called line. Similar apparatus in the two figures is distinguished by adding the symbol indicating prime to Fig. 3 apparatus.

When plug 223 is inserted in jack I28 2. circuit is established from battery through relay 2E9 winding, in Fig. 2, through plug 226 sleeve, the sleeve of jack 128', Fig. 3, through relay i253 winding to ground. Relays 2l9 and I20 Opelate. When relay 2l9 operates the tip of the cord is cut through the upper outer armature and make contact of relay 2I9, the upper outer break contact of relay 2I8, the upper outer break contacts of relay 2H, top winding relay 2I2, armature and M contact relay 2H], armature and M contact relay 2i I to positive battery. In the subscribers extension line circuit the tip circuit for this condition has heretofore been traced through the upper winding of relay I21, upper outer armature and break contact of relay I2 5 to negative battery. Relay 2I2 in Fig. 2 remains on M and relay I 21' in Fig. 3 operates to M. The sequence of events which occur in the line circuit, Fig. 3, after the operation of relay I21 to M, has heretofore been described. The ring circuit is now extended from the lower inner break contact and armature of relay I24, through the ring of jack I28, ring of plug 226, upper inner armature and make contact of relay 2I9, lower outer armature and break contact of relay 2M, through the winding of relay 2I5 to battery operating relay 2I5. The operation of relay 2I5, completes. a circuit from ground on the lower make contact of relay 2I5, through the lower armature relay 2I5, filament lamp 225, through the winding of relay 222 to battery, operating relay 222 and lighting lamp 225 as a signal that the subscriber on the extension line circuit has not yet answered. Relay 222 operated, actuates an audible signal. The operation of relay 2E5 operates relay 2H5 from battery, through relay 2M lower winding, through the upper inner armature and make contact of relay 2l 5, through the upper outer armature and make contact, relay 2l5, through the front contact and upper inner armature of relay 226, through the ring of plug 226, to ground on the lower inner armature and back contact of relay I24. With relay 2M operated the 60 I. P. M. ground connected through the lower inner armature and front contact cannot flash lamp 225 as relay 2I5 is operated and direct ground is furnished to the lamp .on the front contact associated with relay 2I5 lower armature instead of the interrupted ground on relay 2I5 lower armature back contact which functions on recall.

The operator is now ready to ring the called station. To do this the operator operates key RC momentarily. When key RC is operated a circuit is closed from ground, through the upper left-hand armature and front contact of the key, winding of relay 22!, front contact and lower inn-er armature relay 2H3 to battery. Relay 22! looks from ground through its lower armature and front contact. With relay 22I operated, a circuit is prepared for the operation of relay 228, but this relay does not operate as relay M8 was also operated when key RC was operated from ground through the lower armature and front contact key RC through relay 2 I 3 winding'to battery. Relay 2I8 looks from battery through its winding, front contact and lower inner armature relay 2H3, front contact and upper inner armature relay 2H3, ring of plug 226 to ground through the lower inner armature and back contact of relay I24.

With relay 2I8 operated and locked, relay 228 is prevented from operating. The transmission circuit of the cord is cut and closed toward the calling station and a circuit is established for the operation of ringing relay 220 from battery through the lower outer armature and front contact of relay 2I8 through relay 22B winding to ground. Relay 220 is connected to a machine ringing generator which applies ground to the circuit for two seconds and then opens the circuit for four seconds. With relay 2! operated, relay 220 remains operated for two seconds out of every cycle of six seconds duration. During the two second period when relay 220 is operated, a source of twenty cycle alternating current is applied from ground through the front contact and armature of relay 220, top inner armature and front contact of relay 2l8, front contact and top outer armature of relay 2I9 to the tip of plug 226. During the four second period while armature 220 is released, positive battery is supplied through a resistance to the back contact and armature of relay 220 over the path last traced to the plug 226. The ringing path in the extension line circuit has heretofore been described. As has been described heretofore, also, the subscriber responds by operating his power switch IM to the left closing the station loop. A chain of operations heretofore described is set in motion culminating in the extension circuit in the operation of relay I24 which removes ground from the ring of jack I 28. This releases relays 2I5, 2M, 2I8 and 228 in the cord, Fig. 2, extinguishing the lamp, stopping the ringing and cutting the transmitting path in the cord through so that the subscribers may communica e.

During normal communication between the calling and called subscribers, marking and spacing signals are sent to and fro between the stations. When signals are sent from the calling station the following relays respond to the signals:

Fig. 1-HI, H3, H4 and H5 Fig. 2-269 and 2H When signals are sent from the called station the following relays respond to the signals:

Fig. 2-2I2 Fig. 1I2'l, I29, I and I05 The manner in which Fig. 2 cooperates with Figs. 1 and 3 when a break signal is sent from the called station to the calling station will now be described.

We have seen in the description of the operation of the extension line circuit that when a break signal is sent from a station, positive battery is connected to the tip of the line jack. For this condition, therefore, positive battery will be connected to the tip of jack I28 of Fig. 3. This circuit is extended through the tip of plug 226, the upper armature and front contact of relay 2I 9, the break and front contacts associated with the upper armatures of relays 2I8 and 2, the upper Winding of relay 2l2, relay 2W armature and M contact to relay 2 I I armature. When the calling subscriber sends the next marking signal relay 2II operates to M. Positive battery meets positive battery. The current through the top winding of relay 2I2 is reduced to zero. The current through the middle winding of relay 2I2 still persists and relay 2I2 is operated to S before relay 2II can leave its M contact. With relay 2I2 on its S contact negative battery on the armature of relay M2 is connected to the tip of the calling end of the cord through the plug and jack to meet negative battery on the M contact of relay II5 in Fig. 1. Negative battery meets negative battery on each side of the upper winding of relay I21. The current through the winding is reduced to zero and relay I27 is operated to its S contact under the influence of its lower winding. In turn relays I29 and E30 opera to S and the calling station is broken.

When a break signal is sent from the calling station to the called station, when relay H5 operates to its spacing contact as described heretofore, positive battery is connected to the tip of jack I28 in Fig. l, thence through relay 2| I upper winding to relay 2I2 armature. When the next marking signal is sent by the called station, Fig. 3, relay 2 I2 operates to M. Positive battery is connected to each end of relay 2II upper winding. The current in the winding drops to zero and relay 2H operates to its 8 contact under the influence of its lower winding. Negative battery is connected through relay 2 armature over the tip of the calling cord through the tip of plug 225, tip of jack 28 to meet negative battery on the marking contact of relay H5. The current through the upper winding of relay I27 is reduced to zero. Relay I2'I operates to spacing and the break signal is propagated to the called station in a manner similar to that described above for the break signal from the called to the calling station.

Now the manner in which the cord circuit per Fig. 2 cooperates with Fig. l for a recall signal between the calling subscriber and the operator will described.

We have seen that when the calling subscriber sends a recall signal when Fig. l is cooperating with a cord of the type of Fig. 2, wherein the interrupter which performs the flashing is located in the cord itself rather than in the extension line circuit, the interrupter I32 in Fig. 1 is omitted by opening switch I39. Key H0 is cut into the circuit in l by operating switch I41 to contact E42 and switch I22 to contact I45. Under these circumstances we have seen that operation of recall key III} sends four open pulses, the fourth pulse being long. A momentary ground from the third contact on bank I25 was connected to the ring of jack I28 followed by an open. When the ground is connected to the ring of jack I28 it is extended through the ring of plug 220, through the upper inner armatiue and make contact of relay 20 which is operated at this time, through the lower outer armature and back contact of relay 208, which is unoperated, to relay 201 windoperating relay 201. When relay 20'! operates a circuit is closed from the same ground which operated relay 201 through the lower inner front contact and armature of relay 207 through relay lower winding to battery operating relay 203. When relay 208 operates it locks from battery through relay 208 upper winding, upper armature and front contact relay 208, lower armature and back contact relay 205 to ground. Relay 20'! then releases because the ground is removed from the ring circuit at the end of the pulsing period. Ground is connected through the interrupter to the lower inner armature and front contact of relay 208, through the lower inner back contact and armature of relay 201, through the filament of lamp 223 through relay 222 winding to battery flashing lamp 223, indicating a recall by the calling subscriber. The operator operates her typing operating relay 205 and breaking the locking path of relay 208, extinguishing the lamp.

If a disconnect signal is sent by the calling subscriber, we have seen that a permanent ground is connected to the ring of jack I28 and by the circuit heretofore traced to relay 201. Relay 20? remains operated and permanent ground instead of interrupted ground is connected through the lower inner front contact and armature of relay 28! to the lamp. The lamp burns steadily as a disconnect signal.

On the calling end of the cord similarly when the extension circuit Fig. 3 is connected to Fig. 2, the temporary ground for a recall signal operates relay 2I5 which in turn operates relay 2 M, which connects interrupted ground through the lower back contact and armature of relay 2 I5 to lamp which flashes, indicating a recall from the called subscriber. For a disconnect relay 2I5 remains operated lighting lamp 225 steadily as a signal that the called subscriber has disconnected.

The above will serve to describe how the cord per Fig. 2 cooperates with the subscribers extension line circuit of this invention.

In the case of the cords per Figs. 4 and 6 and their respective operators circuits per Figs. 5 and 7, which can also function with this inventon, it will not be necessary to an understanding of the invention herein to describe their operation in detail as in cooperating with the extension line circuit per Fig. 1 or Fig. 3 they function in their well-known manner but we will describe them now in a general way.

As explained above, Fig. 4 is a well-known cord circuit and Fig. 5 its position circuit which will function with the circuit of this invention. When cord circuits of the type of Fig. 4 are used, the interrupter which is used for flashing the lamp for the recall signal is connected to the line circuit, since there is no interrupter in the cord. Key I40 is used in Fig. 1 by operating switches MI to contact Hit and I42 to contact I46. Key H0 is disconnected. For recall four equal length short open and close pulses are sent by key I40. The selector is stepped to the fourth point on the banks. The interrupter I32 is connected to the fourth point of bank I25 as switch I39 is closed. As relay I24 is operated the circuit from interrupted ground is extended through the lower inner front contact and armature of relay I22 to the ring of jack I28, through relay 404 winding to battery. Relay I04 operates and releases intermittently following the interruptions flashing lamp 422 over an obvious circuit. In the case of the calling cord when the called subscriber recalls, relay 409 follows the interruptions and lamp H0 flashes.

To stop the flashing on the calling cord the operator momentarily operates the recall release key. Prior to this operation the sleeve circuit of the answering end of the circuit extends from ground through relay I20 winding in Fig. 1, through the sleeve of jack 528, through the sleeve of plug 46H through the winding of relay 603 to battery. When the key is closed the path through relay I20 winding in Fig. l is shunted through the upper outer make contact and armature of relay 404 as it operates through low resistance ii! to ground. Relay I20 in Fig. 1 momentarily releases, furnishing ground to the selector release magnet which restores the selector to normal, breaking the interrupter path and stopping the flashing.

On the calling end of the cord a similar shunting path is provided when the recall release key is operated through the upper outer front contact and armature of relay 490 as it operates through resistance M2 to ground.

In performing these functions and all other functions involved in this connection the cord per Fig. 4 and its associated position circuit, Fig. 5, operate in their usual well-known manner and further description of it is therefore considered unnecessary as the various cord a'ndposition circuits are not parts of this invention.

Fig. 6 is a third well-known type of cord and Fig. '7 its associated position circuit with which the subscribers extension line circuit of this invention will function. As far as its relation to the extension line circuit supervisory features is concerned, the operation of the cord per Fig. 6 is in general similar to the operation of the cord per Fig. 2 described above and it will therefore not be described in detail here.

What is claimed is:

l. A multisection repeater telegraph extension line circuit comprising a local telegraph station and a terminating circuit with a multisection repeater therebetween, control means at the local station for generating electric impulse trains of difierent lengths, means in said repeater. for propagating said trains, and means in the terminating circuit for discriminating between the trains.

2. A multisection repeater telegraph extension line circuit comprising a local telegraph station and a terminating circuit with a multisection repeater therebetween, interrupter control means at said local station for generating electric impulse trains of different lengths, means in said repeater for propagating said trains, and relay and selector means in said terminating circuit for discriminating between the trains.

3. A multisection repeater telegraph extension line circuit comprising a local telegraph station and a terminating circuit with a multisection repeater therebetween, control means at said 10- cal station for generating electric impulse trains of difierent lengths, means in said repeater for propagating said trains, means in the terminating circuit for discriminating between the trains, and translating means in the terminating circuit operating to translate said trains into signals of a diiferent character for transmission beyond the terminating circuit.

4. A two-path polar subscribers line extension circuit comprising a local telegraph station and a terminating circuit with a multisection repeater therebetween, control means in said station circuit for generating trains of electric impulses of different lengths, means in said repeater for propagating said trains, and means in said terminating circuit for discriminating between the trains.

5. A two-path polar subscribers line extension circuit comprising a local telegraph station and a terminating circuit, interrupter control means at said local station for generating trains of electric impulse of different lengths, and relay means in said terminating circuit for translating said impulse trains into signals different in length from the original impulse trains.

6. A two-path polar subscribers line extension circuit comprising at least one repeater section intermediate a local telegraph station and a terminating circuit, each connected to said extension circuit, signal control means in said local lstation operating to generate trains of electric impulse of different lengths, relay and selector means in said terminating circuit discriminating between said impulse trains, and relay means also in said terminating circuit to translate said trains and relay means therein to propagate signals differing in character fromthe original impulse trains to a connecting circuit.

7. A multisection repeater telegraph extension line circuit comprising a local telegraph station and a central telegraph station terminating circuit, a jack circuit in said terminating circuit arranged to connect to a cooperating circuit, supervisory signal control means in the local telegraph station for generating a supervisory signal of a fixed duration, and relay and selector means in the terminating circuit for changing the duration of the supervisory signal before it is propagated to said cooperating circuit.

8. A multisection repeater telegraph extension line circuit comprising a local telegraph station and a terminating circuit, said line circuit arranged to connect with a cooperating circuit, supervisory signal control means in said telegraph station arranged to propagate recall signals, and independent relay means in said line circuit for receiving break signals propagated simultaneously from said cooperating circuit.

9. A multisection repeater telegraph extension line circuit comprising a local telegraph station and a terminating circuit, means for connecting said line circuit with a cooperating circuit, supervisory signal control means in said telegraph station arranged to propagate disconnect signals, and independent relay means in said line circuit for receiving break signals propagated simultaneously from said cooperating circuit.

10. A multisection repeater telegraph extension line circuit comprising a local telegraph station and a terminating circuit, means for connecting said line circuit with a cooperating circuit, break signal control means in said station for generating an electric impulse of specific duration, supervisory signal control means also in said station for generating a train of electric impulses, relay and selector means in said terminating circuit for translating a supervisory impulse train into a signal of different length before propagation to said cooperating circuit, and relay means also in said circuit for propagating a break signal to the cooperating circuit of substantially the same duration as the generated break signal.

11. A multisection repeater telegraph extension line circuit comprising a local telegraph station loop circuit and a central telegraph station line circuit with a multisection telegraph repeater therebetween, said local telegraph station loop circuit being normally open when idle, a signal in said line circuit for indicating that said local station is calling, means in said circuits for operating said signal in response to the closing of said loop, and means under control of said local station for restoring said signal to its unoperated condition in response to the reopening of said loop.

12. A central telegraph switching station, a local telegraph station, a multisection telegraph repeater circuit connecting said stations, a line signal connected to said circuit at said central station, signal control means at said local station for operating said signal to indicate that said local station is calling, and signal control means also at said local station for restoring said sigcal to the unoperated condition.

13. A subscribers telegraph station, a central telegraph station, a first telegraph repeater station intermediate said subscribers station and said central station, a two-conductor telegraph loop circuit. normally open when idle, connecting said subscribers station and said first repeater station, a two-channel telegraph circuit extending said loop circuit from said first repeater station through a plurality of intermediate repeater stations in tandem, to said central station, a station calling signal connected to said loop at said subscribers station, and calling signal control means connected to said two-channel circuit at said central station for operating said calling signal as an indication to said subscribers station to close said loop.

14. A central telegraph station and a plurality of telegraph repeater stations, a two-channel telegraph circuit connecting said stations in tandern, a subscribers station remote from said central station, a two-conductor telegraph loop circuit, normally open when idle, connecting said subscribers station to the repeater station most remote from said central station to form with said telegraph circuit a multisection repeater subscribers telegraph extension line circuit, and a source of power at said most remote repeater station connected to said loop when said loop circuit is closed.

15. A subscribers telegraph station, a central telegraph station, a plurality of telegraph repeaters in tandem intermediate said stations, a two-wire telegraph loop circuit, normally open when idle, connecting said subscribers station and its nearest repeater station, independent transmitting and receiving telegraph channels extending said loop through said repeaters to said central station, relay means connected to said loop at said subscribers station for receiving a break signal, supervisory signal control means connected to said loop at said subscribers station for operating supervisory signal means connected to said transmitting channel at said central station while said break signal is being received at said subscribers station.

16. A subscribers telegraph station, a central telegraph station, a first telegraph repeater station intermediate said stations, a telegraph line terminating circuit at said central station, a plurality of telegraph repeater stations intermediate said first repeater station and said terminating circuit, a two-conductor telegraph loop circuit, connecting said subscribers station and said first repeater station, a two-channel telegraph repeater circuit connecting said loop circuit to said terminating circuit through the succeeding repeater stations in tandem, calling, supervisory, communication and break signal transmitting means, and calling, communication, and break signal receiving means connected to said loop circuit at said subscribers station, calling, supervisory, communication and break signal receiving means, and communication and break signal transmitting means connected to said terminating circuit at said central station, and means in said circuits for transmitting a supervisory signal from said subscribers station to said supervisory signal receiving means at said central station while said break signal receiving means at said subscribers station is receiving a break signal.

17. A two-channel multisection repeater circuit connecting a plurality of repeater stations in tandem, intermediate a subscribers telegraph station and a central telegraph station, a twoconductor telegraph circuit extending said twochannel circuit to said terminating circuit, a twoconductor telegraph loop circuit, normally open when idle, extending said two-channel circuit to said subscribers station, relay means in said circuits for transmitting and receiving communication signals between said subscribers station and said central station on a half duplex basis, and relay means in said circuit for transmitting supervisory signa s from said subscribers station to said central station on a full duplex oasis.

FRED J. SINGER. 

